JPH0141500B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for coating a metal substrate with a vinylidene fluoride resin film. Attempts have been made to coat metal substrates by utilizing the weather resistance and chemical resistance of vinylidene fluoride resins. Conventionally, a so-called lamination method is known as a method for coating a metal substrate with a vinylidene fluoride resin film. According to this method, an adhesive composition dissolved in a solvent is applied to the surface of a metal substrate to be coated or to one side of a vinylidene fluoride film to a thickness of 1 to 100 μm, and a coating dryer is used at 60 to 200°C. After drying for 0.5 to 30 minutes, vinylidene fluoride film is layered on one or both sides of the metal substrate. This is a method in which this is crimped using a roll laminator, press laminator, etc., heated, pressurized, and then cooled.
In this case, even if the vinylidene fluoride film is stretched, it becomes opaque when the thickness exceeds 10 microns.
The disadvantage is that the color of the underlying colored layer or the metallic luster of the metal substrate cannot be clearly seen. Furthermore, since it is an expensive resin, from this point of view as well, it is desirable to use it as a thin film. On the other hand, the thickness is about 10 μm
Anything below is not only difficult to handle, but also causes endless wrinkles like gold foil, and it is impossible to prevent air from being trapped at the laminated interface. This itself is unsightly in appearance, but on top of that, moisture from the outside world diffuses through the vinylidene fluoride film into the air bubbles and forms blisters, making the appearance even more unsightly. In addition to this, it also has the disadvantage that it is more easily peeled off than the non-bonded parts. Another conventional technique involves the use of vinylidene fluoride paints. If such a paint is used, wrinkles will not occur as in the above-mentioned method. However, even though vinylidene fluoride itself has excellent chemical resistance, it can cause rust due to cracks in the paint film during pressure molding, scratches during application, or pinholes due to evaporation of volatile components after painting. It has the disadvantage that corrosion of the metal base material is unavoidable. In view of the current state of the prior art, the present invention provides a method for coating a metal base material with a vinylidene fluoride resin film without causing wrinkles and allowing the underlying metal surface of the vinylidene fluoride resin layer to be clearly seen. Moreover, it is an object of the present invention to provide a coating method that can suppress corrosion of metal substrates and has good adhesive properties. In the present invention, by heat-pressing a coextruded laminated film having a layer made of vinylidene fluoride resin and an adhesive layer onto a metal substrate, wrinkles do not occur even when the vinylidene fluoride resin film has a thickness of about 1 μm. This is based on the discovery that it can suppress corrosion of metal substrates without causing corrosion, and has good adhesive properties. Examples of the vinylidene fluoride resin in the present invention include vinylidene fluoride homopolymer (hereinafter referred to as PVDF).
), vinylidene fluoride is 50 mol% or more,
Examples include copolymers of this and one or more comonomers that can be copolymerized, and compositions mainly containing at least one of these homopolymers and copolymers. The degree of polymerization and polymerization method of the vinylidene fluoride resin in the present invention are not particularly limited, and any method can be used, but the degree of polymerization obtained by suspension polymerization is preferably 700 to 1300, and more preferably The range of 900 to 1100 is used. The upper limit of the thickness of the vinylidene fluoride resin layer is preferably 10 μm from the top to make the color of the base layer clear.
8 μm, more preferably 5 μm. On the other hand, the lower limit of the thickness is not particularly limited, but in order to sufficiently suppress corrosion of the metal base material, it is preferably 1 μm,
Even more preferably, it is 2 μm. With such a thin film, there is a risk that parts of the metal base material cannot be prevented from being corroded due to microscopic variations in the molding process. There was a fear that the performance would deteriorate, but as shown in the Examples below, extremely excellent chemical resistance was observed. As the adhesive layer to be coextruded and laminated with the vinylidene fluoride resin layer, one layer is sufficient as long as it is an adhesive that can adhere to both the vinylidene fluoride resin and the metal substrate. Preferably, such an adhesive layer is made of methacrylic resin. Examples of the methacrylic resin used in the present invention include methyl methacrylate, ethyl methacrylate, etc., in which the alkyl group has 1 to 4 carbon atoms;
Preferably, a homopolymer consisting of one or two methacrylic acid alkyl esters, a copolymer containing at least one of these at 50 mol% or more, or a graft copolymer containing such a polymer at 50 mol% or more of the matrix resin, or such a polymer. Examples include compositions containing 50 mol% or more. It goes without saying that even if the adhesive layer is capable of adhering to both the vinylidene fluoride resin and the metal base material, if it is insufficient, the adhesive layer may not be one layer, but two or more layers. For example, since the adhesive strength between methacrylic resin and metal base material is somewhat insufficient, a vinyl chloride resin layer is coextruded and laminated on the surface of the methacrylic resin adhesive layer that is not laminated with the vinylidene fluoride resin layer, and this chloride resin layer is laminated by coextrusion. A method in which a vinyl resin layer is laminated on a metal base material is even more preferably used. In addition, the coextruded laminated film may include other layers. If the total thickness of the laminated film is thick enough, it can be handled without any problem during molding and can be laminated onto a metal substrate without wrinkles. The stiff thickness usually needs to be 10 μm or more, preferably 25 μm or more, so that it can be laminated onto a metal substrate more easily. A multilayer laminated film having a vinylidene fluoride resin layer and an adhesive layer is produced by coextrusion molding.
Coextrusion molding methods include, for example, a method in which each layer to be laminated is extruded separately and then laminated outside the die using a roll, etc., and a single extrusion molding method using an extruder with the same number of extruders as the number of layers to be laminated has the same number of grooves as the extruder. A method of supplying to a die and laminating within the die, supplying the required number of extruders to a flux distribution device, laminating in this distribution device,
Known coextrusion methods such as feeding into a die may be used. In the present invention, the vinylidene fluoride resin, which has insufficient adhesion with other resins, is melt-mixed at the adhesive layer and its interface by coextrusion, resulting in a strong bond. It exhibits superior adhesive strength compared to conventional techniques such as the above, but it is also superior in that it does not require the use of toxic organic solvents, as is the case with painting methods. The coextruded laminated film is drafted after the above-mentioned coextrusion in order to reduce the thickness of the vinylidene fluoride resin layer to 10 μm or less, and is further cold stretched if necessary. Such draft conditions vary depending on the resin composition and resin viscosity, so it is difficult to state them uniformly, but for example, when one layer is made of vinylidene fluoride resin and another layer is made of methacrylic resin,
It is carried out at a temperature range of 190 to 280°C, preferably 200 to 240°C, and a draft rate of 5 to 70, preferably 10 to 40. At this time, the vinylidene fluoride resin used has a degree of polymerization in the range of 700 to 1200,
The methacrylic resin has a melt flow index of 0.4 to 16 g/10 minutes, preferably 1 to 8 g/10 minutes.
10 minutes, more preferably 1.5 to 4 g/10 minutes. Here, the melt flow index was determined according to ASTM D1238 at 230°C and a load of 3.8 kg. As another example, in addition to the above two layers, if vinyl chloride resin is laminated,
It is carried out at a resin temperature of 195 to 210°C and a draft rate in the range of 5 to 70, preferably in the range of 10 to 40. At this time, the vinyl chloride resin has a polymerization degree of 700 to 1700, preferably
A range of 1000-1300 is used. Cold stretching is performed by a known method, and relaxation heat treatment is performed as necessary after drafting or stretching.
In that case, it is usually sufficient to heat the mixture at 60 to 100°C for about 5 seconds to 1 minute. The relaxation heat treatment is performed to relieve residual strain caused by drafting or stretching, and there is no need for the relaxation heat treatment if such residual strain does not cause any problem. For example, if there is a soft layer such as soft vinyl chloride between the coextruded laminated film and the steel plate, this layer will deform, so even if there is residual strain, there will be no problem. The shape of the above-mentioned coextrusion film is not limited to a flat plate, but may be in various shapes such as a film cut into a tube and cut open. Various types of metal substrates may be used as the metal base material on which the above-mentioned coextrusion film is laminated. Examples include iron-based metals, aluminum-based metals, copper-based metals, titanium-based metals, and the like. Among these, iron-based metals include steel, electrolytic chromic acid treated steel, steel plated with zinc, aluminum, copper, chromium, tin, lead, etc., or steel plated with alloys thereof. In addition, aluminum-based metals include aluminum alone or various aluminum alloys such as duralumin,
Further examples include aluminum metal containing small amounts of manganese, magnesium, and the like. In the present invention, it is desirable to previously treat the surface of the metal substrate before laminating it with the laminated film in order to improve adhesion. For example, cleaning treatments such as degreasing, surface roughening treatments such as sand blasting, chemical etching, etc. are desirable. An adhesive may be applied to the laminated surface of the metal base material, which has been previously surface-treated or has not been surface-treated, before laminating the metal base material with the laminated film in order to increase the adhesive force with the laminated film. Known adhesives such as acrylic, epoxy, urethane, and rubber adhesives are used as the adhesive. A vinyl chloride resin may be applied onto such a metal base material by a vinyl plastisol method instead of the single vinyl chloride resin layer of the above-mentioned laminated film. The vinyl plastisol method here includes the so-called modified plastisol method and organosol method, in which vinyl chloride resin with a plasticizer added is made into a paste and coated by roll coating, dip coating, knife coating, curtain flow coating, etc. This is a method of coating and heating to form a film. The laminated film is laminated by being pressed against a metal base material. In this case, when using an adhesive between the laminated film and the metal base material, if the adhesive has a sufficient adhesive layer at room temperature, it may be crimped at room temperature, so heating is not necessarily required for crimping. do not have. When an adhesive is not used, a method is employed in which the laminated film is heated to a temperature at which the adhesive layer resin that is in direct contact with the metal surface is substantially melted or softened. At this time, the heating temperature is usually
The temperature is 80 to 250°C, and the pressure is preferably 3 to 300 kg/cm ² for 10 to 180 minutes in the press method. Examples of the present invention will be described in more detail below, but these are merely explanatory materials and are not intended to limit the scope of the present invention. Examples 1 to 7 PVDF (using KF#1000 manufactured by Kureha Chemical Industries) and acrylic resin (using Hypet HBS manufactured by Mitsubishi Rayon) were extruded from separate extruders, and a laminated composite T die (1.3 Composite fluidization was performed within a width of m width) and extrusion was carried out in layers. Draft this at 40
It was drafted at twice the original temperature and cooled by taking it over with a roller at 60°C. At this time, the lip resin temperature was 220°C.
Then, the thickness of the laminated film was 50 μm, and the thickness of the PVDF layer was 1 μm.
A laminated film of m was obtained. Similarly, the thickness of the PVDF layer is 2 μm, 3 μm, 4 μm, 6 μm, and 8 μm, respectively.
m, 10 μm, and the thickness of the laminated film is 50 μm.
I also got the film. On the other hand, each side of a steel plate with a thickness of 0.5 mm has a thickness of
A 20μ thick zinc plating was applied, and a 0.1μ thick chemical conversion coating layer was applied to each surface by zinc phosphate treatment. The acrylic resin adhesive "Corona Paint" (trade name related to the manufacture of Nikko Vicks) was roll-coated to a thickness of 10 μm on the zinc phosphate-treated steel plate, and the steel plate was baked at a temperature of 200°C. This resin-coated steel plate was heated to about 160° C., and the above-mentioned laminated film was pressure-fused with a roll. The following tests were conducted on these resin-coated steel sheets, and the results are shown in Table 1. (1) Chemical resistance 0.5 cc of the various chemical solutions shown in Table 1 was pipetted onto the film, covered with a watch glass, and left in the air for 24 hours. As a result, ◎ indicates that there is no change at all on the film surface, ○ indicates that there is a slight mark, △ indicates that there is a slight mark and internal whitening is observed on the acrylic resin layer, and △ indicates that there is a significant pattern mark on the acrylic resin layer. When internal whitening was observed, it was marked as ×. (2) Film formability After coating the steel plate, visually observe whether wrinkles have formed. Examples 8 to 14 Each of the steel plates used in Examples 1 to 7 was coated with an acrylic adhesive, and after baking, a paint was applied to a thickness of 0.2 mm and further baked at about 200°C. When each of the laminated films used in Examples 1 to 7 was pressure-fused to this coated steel plate in the same manner as in Examples 1 to 7, even better adhesion was obtained, but the same as in Examples 1 to 7. The results were obtained.

【table】

[Table] Comparative Examples 1 to 9 A galvanized iron plate was subjected to a chemical conversion treatment with zinc phosphate, and an acrylic resin adhesive "Corona Paint" (trade name related to the manufacture of Nihonbix) was applied thereon by roll coating. Baked at a steel plate temperature of 200℃. The thickness of this acrylic resin layer is 60μ, including the thickness of the PVDF layer shown in Table 1, which is laminated on top of it.
If necessary, the coating and baking were repeated. A PVDF film having the thickness shown in Table 1 (KF #1000 manufactured by Kureha Chemical Industry Co., Ltd. was used) was roll coated thereon at a roll surface temperature of 160° C. and a pressure of 10 kg/cm ² . As shown in Table 1, the results show that the thinner the PVDF layer, the more wrinkles occur. Further, when the film was thick, its transparency was lower than that of Examples 1 to 7. Comparative Examples 10 to 16 Galvanized iron plates were subjected to chemical conversion treatment with zinc phosphate. On top of that is an acrylic resin adhesive called “Corona Paint.”
(trade name related to the manufacture of Nihonbix) was applied by roll coating and baked at a steel plate temperature of 200°C. Coating and baking were repeated as necessary so that the thickness of this acrylic resin layer, including the thickness of the PVDF layer laminated thereon as shown in Table 1, was 60 μm. Vinylidene fluoride organosol was applied onto this acrylic resin layer using a roll, dried at 135°C for 15 minutes, and then baked at 240°C for 5 minutes.
Painting and baking were repeated as necessary to achieve the thickness of the PVDF layer shown in Table 1. The results are in Table 1
As shown in Figure 2, if the PVDF layer is thin, it is difficult to form a film, and even if it is possible to form a film, if it is thin, the chemical resistance will be insufficient. Furthermore, when the thickness reaches a certain level of chemical resistance, the transparency is insufficient. As shown in the above examples, the vinylidene fluoride resin layer according to the present invention can be on the order of several μm, so it can be made as thin as or even thinner than coating, which saves resources. . Moreover, compared to coated materials, it has better chemical resistance because there are no pinholes. In addition, it does not wrinkle and has excellent appearance and durability, and is especially suitable for construction materials such as outdoor roofs, external walls, and anti-contamination internal walls, packaging cans for storing medicines, foods, etc.
It is useful for various industries including transportation equipment such as automobiles and ships.

Claims (1)

[Scope of Claims] 1. A coextruded laminated film comprising a layer made of vinylidene fluoride resin film having a thickness of 10 μm or less and an adhesive layer, the total thickness of which is at least 10 μm or more. A method for coating a metal base material with a resin, the method comprising: pressure-bonding the above onto the metal base material. 2. The method for coating a metal substrate with resin according to claim 1, wherein the layer made of vinylidene fluoride resin film has a thickness of 2 μm or more.